The invention relates to heating of a fuel feed line for an engine, e.g. a vehicular engine, and more particularly to an improved fuel line heating system wherein a heating element is positioned directly inside the fuel line.
In extremely cold environments, there are problems of fuel freezing or partially solidifying in fuel lines. Problems are particularly serious with diesel fuel, wherein the content of paraffins has been increasing in recent years. Very low temperatures in such fuels can cause a sludge to form, hindering fuel flow.
Previously, approaches to this problem have involved heating elements applied to fuel lines as tracers, i.e. positioned on the outside of the fuel line coextensive with the line. The electrical resistance elements were applied to vehicle fuel lines and hydraulic lines on aircraft and other equipment which often encounter extremely low temperatures.
The problem with this prior art approach has been a lack of efficiency in transfer of heat from the exterior heating element to the fuel inside the line. The problem of heat transfer was even more serious with vehicular fuel lines covered with steel wires for protection. There has been no efficient way to bring the heat from the heating element to the fuel in the line, and to avoid considerable waste of heat to the surrounding air.
Previously, the positioning of electrical resistance heating wire inside a fuel line did not seem feasible because of the apparent danger of fuel ignition in the event of wire breakage or other failures. The concept of incorporating the heating wire directly inside the fuel line apparently has not previously been suggested because of such considerations.
It is an object of the present invention to improve the efficiency of fuel line heating, as well as the simplicity and cost effectiveness of a fuel line heating system, by incorporating the special type of electrical heating element directly within the fuel line.